When to plant · 38 cities · zones 5b–6a
When to plant basil in Illinois
Start Genovese Basil seeds indoors around Mar 20 and transplant around May 1 — the Illinois statewide median, counted from a last spring frost of Apr 17 across 1,402 ZIP codes and 192 NOAA stations.
The rule: Basil is damaged below about 50 °F, well before frost: transplant two weeks after the last frost, not on it.
Illinois basil, by step
Statewide median last frost Apr 17, first fall frost Oct 21, 2027 season. Each cultivar's own indoor lead time and days to maturity, same engine as the Plan Builder.
| Cultivar | Start indoors | Plant out | First harvest | Days |
|---|---|---|---|---|
| Genovese BasilGenovese | Mar 20 | May 1 | Jun 30 | 60 from transplant |
Tight means first harvest lands within two weeks of the median first fall frost. Statewide dates are the ZIP-weighted median of every NOAA 1991–2020 station Illinois's ZIP codes resolve to.
Basil in Illinois, city by city
Genovese Basil, scheduled from each city's nearest NOAA station — the same dates as its frost page.
| City | Last frost | Start indoors | Plant out | First harvest |
|---|---|---|---|---|
| Chicagozone 6a | Apr 10 | Mar 13 | Apr 24 | Jun 23 |
| Aurorazone 5b | Apr 19 | Mar 22 | May 3 | Jul 2 |
| Napervillezone 5b | Apr 28 | Mar 31 | May 12 | Jul 11 |
| Jolietzone 5b | Apr 19 | Mar 22 | May 3 | Jul 2 |
| Rockfordzone 5b | Apr 24 | Mar 27 | May 8 | Jul 7 |
| Elginzone 5b | Apr 26 | Mar 29 | May 10 | Jul 9 |
| Springfieldzone 6a | Apr 15 | Mar 18 | Apr 29 | Jun 28 |
| Peoriazone 6a | Apr 16 | Mar 19 | Apr 30 | Jun 29 |
| Champaignzone 6a | Apr 15 | Mar 18 | Apr 29 | Jun 28 |
| Waukeganzone 6a | Apr 30 | Apr 2 | May 14 | Jul 13 |
| Cicerozone 6a | Apr 11 | Mar 14 | Apr 25 | Jun 24 |
| Bloomingtonzone 6a | Apr 21 | Mar 24 | May 5 | Jul 4 |
| Schaumburgzone 5b | Apr 30 | Apr 2 | May 14 | Jul 13 |
| Evanstonzone 6a | Apr 26 | Mar 29 | May 10 | Jul 9 |
| Arlington Heightszone 6a | Apr 19 | Mar 22 | May 3 | Jul 2 |
| Bolingbrookzone 6a | Apr 20 | Mar 23 | May 4 | Jul 3 |
| Decaturzone 6a | Apr 14 | Mar 17 | Apr 28 | Jun 27 |
| Palatinezone 5b | Apr 25 | Mar 28 | May 9 | Jul 8 |
| Skokiezone 6a | Apr 26 | Mar 29 | May 10 | Jul 9 |
| Des Plaineszone 6a | Apr 16 | Mar 19 | Apr 30 | Jun 29 |
| Orland Parkzone 6a | Apr 20 | Mar 23 | May 4 | Jul 3 |
| Oak Lawnzone 6a | Apr 10 | Mar 13 | Apr 24 | Jun 23 |
| Mount Prospectzone 6a | Apr 19 | Mar 22 | May 3 | Jul 2 |
| Berwynzone 6a | Apr 11 | Mar 14 | Apr 25 | Jun 24 |
| Tinley Parkzone 6a | Apr 23 | Mar 26 | May 7 | Jul 6 |
| Wheatonzone 5b | Apr 28 | Mar 31 | May 12 | Jul 11 |
| Normalzone 6a | Apr 25 | Mar 28 | May 9 | Jul 8 |
| Oak Parkzone 6a | Apr 11 | Mar 14 | Apr 25 | Jun 24 |
| Hoffman Estateszone 5b | Apr 30 | Apr 2 | May 14 | Jul 13 |
| Downers Grovezone 6a | Apr 28 | Mar 31 | May 12 | Jul 11 |
| Plainfieldzone 5b | Apr 20 | Mar 23 | May 4 | Jul 3 |
| Glenviewzone 6a | Apr 19 | Mar 22 | May 3 | Jul 2 |
| Elmhurstzone 6a | Apr 16 | Mar 19 | Apr 30 | Jun 29 |
| Lombardzone 6a | Apr 28 | Mar 31 | May 12 | Jul 11 |
| Buffalo Grovezone 6a | Apr 19 | Mar 22 | May 3 | Jul 2 |
| Molinezone 5b | Apr 24 | Mar 27 | May 8 | Jul 7 |
| Crystal Lakezone 5b | May 1 | Apr 3 | May 15 | Jul 14 |
| Romeovillezone 6a | Apr 20 | Mar 23 | May 4 | Jul 3 |
What these basil become
What Illinois basil need
Genovese Sweet Basil Seed
The large-leaf, low-anise Italian basil that pesto is defined by. Thai and lemon basils are good plants and wrong ingredients.
Organic Seed Starter Potting MixMust have
Seed-starting mix is not potting soil with a nicer label — it is finer, lighter, and low in nutrients on purpose, because a seedling's first roots want air and moisture, not fertiliser.
T8 Full-Spectrum Grow Lights, 1 ft 4-packMust have
A south window in March delivers a fraction of the light a pepper seedling needs, and the plant tells you by stretching. Two inches of LED above the canopy for 16 hours a day fixes it permanently.
5-Gallon Fabric Grow Bags, 5-Pack
Fabric pots air-prune roots and drain faster than a plastic pot can, which is the entire reason container tomatoes fail. Five gallons is the honest minimum for a pepper; a tomato wants ten.
Ocean Forest Potting SoilMust have
Pre-charged with enough nutrition to carry a transplant for its first month without feeding, which is exactly the window when most container plants stall.
6" Micro-Tip Pruning SnipsMust have
Ninety percent of sauce-garden cutting is snipping a pepper stem or a basil node, and a fine-tipped snip does it better than any pruner. Pulling peppers by hand tears the branch.
Mesh Strainers, Stainless, 3-Count
The last pass before bottling. A fine mesh catches the skin fragments and seed shards that make a hot sauce gritty and clog a woozy bottle's dripper insert.
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Basil in Illinois: questions
When should I plant basil in Illinois?
Transplant around May 1 at the statewide median; across the state that date runs from Apr 21 in the warmest tenth of Illinois's ZIP codes to May 11 in the coldest. To cut the freeze risk to one year in ten, count from May 3 instead of the median last frost. Use the city table for your own town.
When do I start basil seeds indoors in Illinois?
Around Mar 20 for Genovese Basil: 4 weeks before the statewide median last frost, on soil held at 70–80 °F.
When is the last frost in Illinois?
The ZIP-weighted median of NOAA 1991–2020 station medians is Apr 17. In the warmest tenth of Illinois's ZIP codes the median last frost falls on or before Apr 7; in the coldest tenth, on or after Apr 27.
When will Illinois basil be ready to harvest?
Genovese Basil planted on the statewide date is ready around Jun 30: 60 days from transplant.
More for Illinois
- When to plant tomatoes
- When to plant peppers
- When to plant tomatillos
- When to plant onions
- When to plant cilantro
- When to plant carrots
- When to plant mustard greens
Basil in every state → · Illinois frost dates → · How frost-date math works →